Will Scott Brown's victory turn Obama into a foreign-policy president?

If the most-doomsaying Democrats are right about the special election in Massachusetts—that it means the end of health care reform and much of the liberal agenda generally—then Barack Obama may turn into something he never wanted or expected to be: a foreign-policy president.

External factors—Afghanistan, Yemen, Haiti, and the continuing threats from Iran, international terrorism, and global financial turmoil—are pushing him farther in this direction than he'd like in any case.

But the frustrations of domestic politics—the Republicans' willful obstructionism, the Senate's rule that allows filibusters without actually filibustering, the schisms within his own party, the endless howl of cable newscasts—make the immersion into foreign affairs look like an alluring prospect.

Bill Clinton entered the White House with so little interest in matters beyond the water's edge that he ended the CIA's daily presidential briefings and instructed his national security adviser, Anthony Lake, to keep those issues as far away from the Oval Office as possible. But after his own health-care disaster, and as foreign crises piled up and required his attention, he suddenly took great interest and handled them with increasing skill.

All presidents succumb to this temptation to some degree. Constitutionally and practically, they're allowed much more leeway in foreign affairs—and thus more opportunity to display the qualities of executive leadership. Congress will almost always pony up the necessary funds, especially if "supporting the troops" is involved (as was seen even during the height of opposition to George W. Bush's Iraq policies). Should a majority of Democrats grow weary of, say, the war in Afghanistan, enough Republicans can be counted on to take up the slack, no matter how fiercely they might oppose Obama on other issues.

The military budget usually transcends party-line squabbles as well. In last year's Senate fight over the Air Force's F-22 fighter jet, 15 Republicans voted with Obama to kill the program, and 15 Democrats voted against him to keep it going. (A more decisive influence here was whether one of the plane's contractors was based in a senator's home state.)

Still, foreign affairs can insulate a president only so much from political hailstorms. Obama sent two of his top officials—his national security adviser, Gen. Jim Jones, and the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen—to Moscow Wednesday to put the penultimate touches on a new strategic arms-reduction treaty with Russia. However, ratifying a treaty requires a two-thirds majority in the Senate—not just 60 votes but 67. Many doubted whether Obama could eke such a margin from this Senate before this week; if (again, if) Scott Brown's victory stiffens the Republicans' resolve to block everything that Obama puts on the docket, then the chances of passage dim further.

Prospects also seem very grim for U.S. participation in any international accord involving treaties or vast sums of money, not least an accord on limiting climate change (thus giving India and China full sway to avoid moderating their own behavior).

Besides, it's not clear how much political traction Obama could gain from overseas ventures in any case. In the post-Cold War world, with the fracturing of power and the decline of influence by any one country or bloc, the problems that he faces are simply harder—more impervious to military, economic, or diplomatic pressure—than they would have been 20 to 50 years ago.

One might imagine that U.S. allies, who greeted Obama's victory with such relief and even glee, might help him out in a foreign crisis, to boost his standing and help avoid the prospect of dealing with another W. or worse in the White House.