Here's what the United States has done so far in an attempt to deter further Russian incursions into Ukraine: applied two rounds of economic sanctions and asked Congress to approve $1 billion in loan guarantees for Kiev.
Here's what President Barack Obama says he won't do: "We are not going to be getting into a military excursion in Ukraine," he told a television station in San Diego last week.
The president's careful response and unwillingness to consider military intervention has met with general support from other Democrats. But Republicans have been sharply critical.
"This is the ultimate result of a feckless foreign policy in which nobody believes in America's strength anymore," Sen. John McCain, R-Ariz., charged this month.
The sniping is no surprise given the partisan divide in Washington. But would a Republican in the White House instead of Obama actually plot a different course? That would depend entirely on which Republican we're talking about. The GOP has long been divided on foreign policy, and Ukraine has exposed fault lines that are likely to grow as the Republicans' 2016 nomination contest nears.
On foreign policy in general, and on Ukraine in particular, Republicans fall into three camps: hawks, realists and libertarians.
Let's start with the hawks. McCain, the hawk's leading voice on Ukraine, has been warning against a resurgent Russia at least since his 2000 presidential campaign, when he called for sanctions against Putin over Russia's actions in Chechnya. In the current crisis, he is still not calling for U.S. boots on the ground, but he has called for immediate shipments of small arms and ammunition to Kiev, as well as U.S. intelligence-sharing. "The United States should not be imposing an arms embargo on a victim of aggression," he said last week.
Sen. Marco Rubio, R-Fla., a younger hawk, has gone a step further, calling not only for military aid to Kiev but also for suspending cooperation with Russia on other diplomatic projects, including negotiations with Iran. "Put simply, Russia should no longer be considered a responsible partner on any major international issue," Rubio wrote last week in what amounted to a call for a new Cold War.
William Kristol, editor of the Weekly Standard, may be the most hawkish of the hawks. Last week, he told CNN that "deploying ground troops . . . should not be ruled out."
Closer to the center of the GOP is moderate conservative Sen. Bob Corker, R-Tenn., the top Republican on the Senate Foreign Relations Committee and a realist when it comes to foreign policy.