Ben Sasse is the toast of the national tea party movement today. But it may be as much a marriage of convenience as anything else.

Republican Senate hopeful Ben Sasse, center, laughs with Rep. Jeff Fortenberry, R-Neb., left, and Neb. Gov. Dave Heineman in Lincoln, Neb., Tuesday, May 13, 2014, after winning his party's primary election. (AP Photo)

The newly minted Republican nominee for the U.S. Senate in Nebraska is being celebrated by national tea party groups like the Club for Growth and Senate Conservatives Fund, which spent big money to help him win on Tuesday. But on some big issues, Sasse hasn't always been aligned with the tea party, leading some Republicans to question whether right-leaning groups that backed him were more interested in notching a win in a tough election cycle than electing a staunch defender of their causes.

"It is an interesting choice because Ben Sasse isn’t a pure tea party conservative that outside groups usually endorse," said Republican strategist Ron Bonjean. "But these groups are looking for some high-profile victories this year and stood behind Sasse despite some more moderate leanings and ties to D.C."

Take Medicare Part D, for example. The prescription drug benefit that passed in 2003 earned the ire of the Club for Growth, which spent nearly $500,000 helping Sasse defeat state treasurer Shane Osborn (R) and wealthy banker Sid Dinsdale (R). The group has called Part D an "abomination."

In 2009, Sasse wrote an op-ed highlighting the success of the program, saying it "is (or should be) a policymaker's dream." When asked about it earlier this year by The Washington Post, the group said it disagreed with the op-ed's content.

Health care was a focal point in the primary campaign, even though Osborn and Sasse both favored repealing the law. Osborn raised doubts about Sasse's declared opposition to Obamacare by pointing to a speech he made in 2010.

In the speech in which Sasse criticized the health-care law, he said "what we passed in March is an important first step on thinking about the coverage problem in the American health care system. But, the underlying problems that drive the growth of uninsurance are not being addressed by ducking the larger entitlement problems."

Sasse's campaign denied that he was calling the law a good first step and was referring to the national debate about health care. But the words he used are probably not what you'd hear from staunch Obamacare opponents like Sens. Ted Cruz (R-Tex.) and Mike Lee (R-Utah), who each campaigned for Sasse in the primary.

Sasse, unlike many insurgent tea party candidates, has spent time in the GOP establishment. The current president of Midland University, Sasse worked in the administration of George W. Bush. He was also once a visiting scholar at the center-left Brookings Institution.

While he tussled with Senate Minority Leader Mitch McConnell (R-Ky.) in the campaign, Sasse ultimately told MSNBC on Tuesday that he'd be comfortable backing McConnell as the Republican leader. The Senate Conservatives Fund, a group that spent hundreds of thousands to back Sasse, is supporting McConnell's primary opponent.

Policy differences between Sasse and his opponent Osborn were slight. That led some to conclude that the Osborn's support from some in the GOP establishment prompted tea party groups to jump in for Sasse.

"Simply put, Shane Osborn was backed by the Republican establishment and Ben Sasse was not," said Bonjean.

The tea party/establishment divide isn't always clear cut -- or even permanent. Sen. Marco Rubio (R-Fla.) and New Jersey Gov. Chris Christie (R), for example, enjoyed tea party support in the past but have now come to be viewed more as parts of the GOP establishment.

National tea party groups are in the midst of what is shaping up as a tough election cycle. It's entirely possible that despite drawing many tea party challengers, no Republican senator will lose in a primary this year. In each of the last two cycles, that has not been the case.

The conservative groups that backed Sasse insist that his strong commitment to repealing Obamacare in the campaign and his constitutional conservative approach is what won them over -- not desperation for a win.

"Ben clearly articulated a conservative vision to Nebraska voters who rewarded him with their votes. Club members strongly responded to our appeal for support for Sasse and we’re confident that he’ll be a champion of economic freedom when he is elected to the Senate in November," said Club for Growth President Chris Chocola.

In a memo issued after Sasse won, his campaign signaled he would not be an agitator in the mold of Cruz or former senator Jim DeMint (R-S.C.) -- tea party heroes who won in previous years and repeatedly picked fights with GOP colleagues.

"Conservatives will be thrilled with Ben Sasse as a U.S. senator if they are looking for a leader who will propose and fight for conservative solutions from a constitutional perspective, but they shouldn't expect him to adopt an instinctual reaction of ‘no’; nor should they expect that he will go out of his way to annoy establishment GOP leaders," the memo said. "There are certainly times he will take them on as Sen. Coburn did a decade ago over earmarks, but he will also choose his battles carefully."

Sasse clearly benefited from the support of the national tea party groups, which spent big on his behalf. And they benefited from him by being able to show their donors a win.

Just how much of that symbiosis was rooted in ideology will remain open to debate.