One of President Barack Obama's more under-reported achievements has been his ability to corral Democratic votes in Congress.
When he has asked them to jump, Democratic senators and members of Congress have essentially answered, "How high?" -- on the stimulus, health care, immigration, the 2010 deal to extend the Bush tax cuts, the 2012 fiscal-cliff deal to end them for the wealthy, and controversial nominations.
Yes, Democrats griped about legislative imperfections (they wanted a public option for health care). Yes, many of them took tough votes (see the 2010 midterms). But always in the end, they supported their president and their party, enabling Obama to rack up plenty of first-term legislative achievements.
That is until now.
Twice in the past two weeks, congressional Democrats have broken with Obama on key issues -- the first time this has happened during Obama's four-plus years in the White House.
Last week, Obama's Democratic allies on Capitol Hill appeared unwilling to support his effort to get congressional authorization to use force against Syria. (After defeat of that authorization looked likely, the United States struck a diplomatic deal with Russia to seize Syria's chemical weapons.)
Then on Sunday, the White House announced that Obama's preferred pick to be the next chair of the Federal Reserve -- former White House economic adviser Larry Summers -- withdrew from consideration.
Why? Summers didn't have enough support from Senate Democrats. "[Summers] concluded that the White House was ... unlikely to overcome opposition to his candidacy from many of the same Democrats, who view him as an opponent of stronger financial regulation, according to supporters who insisted on anonymity to describe confidential conversations with him," the New York Times writes.
These Democratic defections could be isolated events; after all, military action in Syria was unpopular with most Americans, and Summers had plenty of enemies, especially on the left.
Then again, there are reasons why the defections might signal future struggles for the second-term president.
For one thing, a president whose job-approval rating stands at 45 percent in the latest NBC/WSJ poll isn't going to have much sway with the public, including members of his own party who are serving in Congress.
“There is no question that a president below 45% job approval starts having more problems with the bully pulpit,” says Republican pollster Bill McInturff, who co-conducts the NBC/WSJ poll.
In addition, second terms have been challenging times for all re-elected presidents since the 22nd Amendment limited them to two terms. The logic: With a lame duck in the White House, Congress begins turning its attention to the next elections -- midterm and presidential.
Indeed, George W. Bush's sway inside his own Republican Party came to an end not after his failed attempt to partially privatize Social Security or his handling of Hurricane Katrina -- but rather the conservative revolt against his pick to place Harriet Miers on the Supreme Court.
But it's just not Obama or second-term presidents.
House Speaker John Boehner also has struggled to rally support from his own congressional rank-and-file on several issues. With two of Washington's most important figures seemingly weakened, it sets the stage for potential chaos in the upcoming budget fights on Capitol Hill.
“I’ve been here for 20 years, and I’ve never seen so much of a repudiation of the conventional sources of power in the legislative or executive branch,” Rep. Jim Moran, D-VA, told the Washington Post. “It portends for a much more chaotic fall,” he said.