For all of their vehement disagreement over policy, advocates and opponents of American diplomatic engagement with Damascus typically share an underlying conviction: Syrian President Bashar Assad holds the key to achieving high priority U.S. foreign policy objectives, whether it be Israeli-Palestinian peace, stability in Iraq or the containment of Iran. Engagers and disengagers differ sharply on how to catch this golden goose, but they are chasing the same imaginary bird. Assad can neither be bribed nor intimidated into making a "strategic realignment" until he first reconciles with the Syrian people.
Syria is the only majority Sunni Muslim polity in the modern era to be ruled by a largely heterodox Muslim governing elite (in this case, Alawite). Although critics of the Assad regime often make far too much of this peculiarity, the very idea of a "heretical" Islamic sect governing the faithful carries an enormous stigma in the predominantly Sunni Middle East (the last time it happened saw the mass conversion of 16th century Iran to Shiite Islam).
This scarlet letter renders the Assad regime uniquely vulnerable to external subversion. Although Syria's exclusionary power structure is somewhat similar to that of Baathist Iraq, where a Sunni-dominated elite ruled over a majority Shiite population, its foreign policy implications are a world apart. The minoritarian character of the Iraqi regime was a strategic asset for Saddam Hussein insofar as fear of empowering Shiites (and Kurds) dissuaded hostile state and non-state actors in the surrounding Sunni Arab world from subverting his rule. The sectarian composition of Syria's governing elite has the reverse effect.
That Alawite political hegemony in Syria has endured for four decades is a marvel of political engineering that defies bulleted summation, but the essential elements include a powerful state that restricts the aggregation of independent political and socio-economic power, a secular nationalist ideology that abnegates communal solidarities, a development model that cultivates cross-cutting loyalties (however inefficiently), and an adventuresome foreign policy calibrated to defuse the threat of sectarian mobilization.
The latter is centered on strategic alignments (today with Iran, previously with the Soviet Union) that give the Syrian regime leverage over potentially meddlesome foreign adversaries and enable it to sponsor regional causes that resonate with the Sunni Arab street. The fact that non-Syrian branches of the Sunni Muslim Brotherhood are friendly with Assad's "apostate regime" and that al-Qaeda largely ignores him (despite many notable Syrians in its leadership) is entirely the result of Assad's demonstrable anti-Zionist and anti-American credentials.
It is not difficult to imagine the kind of trouble that would arise if Assad were to abandon the protections afforded by his foreign policy choices. Even if Israel were willing to give up the Golan Heights, a Syrian peace treaty with the Jewish state would inevitably mean sacrificing the Assad regime's anti-Zionist pedigree, obviating its primary justification for autocratic rule, and abandoning the rights of some 400,000 predominantly Sunni Palestinian refugees in Syria, a combination of factors with great potential to synergize with sectarian resentments at home and abroad. Fully ending Syria's logistical support for jihadist infiltration into Iraq would leave the regime vulnerable to subversion by al-Qaeda. For an Alawite-dominated regime that oppresses a majority Sunni constituency at home, facilitating the rule of an independent Sunni-led Lebanese political coalition a few hours drive from Damascus would be sheer madness (this is precisely what the 2005 assassination of former Lebanese Prime Minister Rafiq Hariri was designed to prevent).
Successive American administrations have been slow to recognize the strategic imperatives of Alawite hegemony in Damascus, in part because the preferences of Syria's leadership are not intrinsically extremist. Most Syrian Alawites are relatively secular, view Islamism as the primary threat to their security, and are less emotionally invested in the Israeli-Palestinian conflict than their Sunni countrymen. Arguably the most culturally Westernized Arab head of state, Assad strikes many American visitors as an eminently reasonable man, thrust by circumstance into an unsavory family business, who honestly desires improved ties with Washington.
This may well be true, but it is irrelevant to the Syrian regime's sober calculation of political risk. Whatever its intentions, a governing elite whose claim to speak for the entirety of its people is so exceptionally weak (even by Middle East standards) cannot follow in the footsteps of Egypt and Jordan. If positive or negative external incentives could lead the Assad regime down this path, it would have happened in the 1990s (when American recognition of Syrian hegemony in Lebanon and offers of economic and military aid were on the table) or in the aftermath of the Hariri assassination (when Syria's diplomatic isolation reached its zenith).
In principle, Assad could pave the way for a strategic re-alignment by first transitioning to a more representative and accountable form of authoritarian governance (to diffuse perceived responsibility for foreign policy away from the Alawite elite, channel dissent into manageable forms of political expression, etc.). In practice, it's not clear that the regime is capable of undertaking such a political opening, and even less clear that such an opening would sufficiently reduce the dangers of dramatic foreign policy change. Even if the regime managed to contain the ensuing threat of violent insurrection and preside over a period of respectable aid-fueled economic growth, the recent uprising in Tunisia was a stark reminder that this is no guarantee of popular quiescence even in the most homogenous and politically placid of Arab states.
This is not to say that the Obama administration shouldn't normalize ties with Syria, only that the pace and scope of normalization shouldn't be predicated on the deferred promise of its strategic realignment. The Syrian regime has always been eager to cultivate as warm a relationship with Washington as its strategic positioning will allow, offering reversible palliatives (e.g. "reining in" Hezbollah) as needed. Returning an American ambassador to Damascus and pretending that Syria isn't bullying Lebanon are warranted only if these quid pro quos advance American interests in the here and now, not the hereafter.
Unfortunately, Assad probably won't have to meet that benchmark, as the dream of "turning" Syria (and the imagined benefits thereof) won't die easily in Washington. A resumption of high-profile Israeli-Syrian talks that go nowhere may not advance U.S. interests, but it will give a boost to an American president facing uncertain re-election and desperate for a short-term foreign policy "success."
 Syrian figures in al-Qaeda are easily recognizable by the surname "Al-Suri" (the Syrian) in their noms de guerre. Notable examples include Abu Musab al-Suri, a major al-Qaeda ideologue; Ghazawan al-Suri, the leader of al-Qaeda in Mosul captured in 2007; Abu Zaid al-Suri, a deputy leader of al-Qaeda in the Iraqi town of Rawah, captured in 2006; Abu Layla al Suri, the leader of al-Qaeda in Diyala, killed in 2008.
 Assad has acknowledged that he would be unable to consent to such terms, cautioning that a Syrian peace treaty with Israel would "not mean trade and normal relations" until the Palestinian refugee problem is resolved. "Peace with Israel possible, says Syria's Assad," Reuters, 9 March 2009.