Sen. Bill Cassidy signaled on Monday that he could become a thorn in the side of President Donald Trump now that he no longer has to deal with the pressures of reelection in his home state of Louisiana.

Cassidy failed to make it into the runoff after a Republican Senate primary over the weekend following withering attacks from Trump, becoming the first elected senator to lose renomination since Richard Lugar in 2012. Cassidy now has roughly eight months remaining in office while holding tremendous power over legislation in the Senate, as well as Trump’s nominees for federal offices, including to key health posts while serving as chairman of the Senate Health, Education, Labor and Pensions Committee.

And even though he’s not explicitly threatening to derail Trump’s agenda, the senator is not being shy about reminding everyone about his loyalty to the U.S. Constitution, rather than to just one man.

“People want me to say negative things, I’m saying positive things – positive things that may reflect upon the current circumstance, but it’s coming from my heart about making my country a better place,” Cassidy told reporters Monday.

“My kind of hierarchy is loyalty to the Constitution, loyalty to the people of the United States, loyalty to my state, loyalty to my country, and so, in that, is holding people accountable,” he added.

Moments later, when asked about Trump announcing a $1.8 billion taxpayer-fueled fund for people who claim to be victims of government “weaponization,” potentially including supporters convicted over the Jan. 6, 2021, riot at the U.S. Capitol, Cassidy didn’t hold back, joining a bipartisan chorus of criticism.

“We are a nation of laws. You can’t just make up things whole piece,” said Cassidy, who voted to convict Trump in the impeachment trial over his Jan. 6 actions. “People are concerned about making ends meet, not about putting a slush fund together without a legal precedent.”

It’s not clear yet what approach Cassidy will take in his final months in office, but he’s got plenty of opportunities to make his voice heard, including on the effort to limit U.S. hostilities against Iran without congressional authorization, Trump’s economic policies and some high-profile nominees such as for labor secretary or U.S. surgeon general.

Cassidy could also pose a problem for Republicans trying to pass funding for Trump’s planned ballroom project at the White House. The senator told NOTUS he doesn’t support including hundreds of millions for security for a new White House ballroom as it currently stands in a party-line reconciliation package.

“They just kind of made that number up. So, from what I know now, I will not be voting for the ballroom fund,” Cassidy said Tuesday, following his primary loss.

Cassidy could also make life more difficult for Health and Human Services Secretary Robert F. Kennedy Jr. and his efforts to challenge public health consensus about the safety of vaccines. Kennedy wouldn’t be in the position had it not been for Cassidy, a medical doctor who has faced intense criticism for his vote to confirm Kennedy as health secretary. The two men have clashed over vaccine safety before, and Cassidy has the power to drag Kennedy back before his committee as part of his congressional oversight responsibilities.

Asked Monday if he planned to hold Kennedy accountable for his actions at HHS, Cassidy said, “Absolutely, I’ll hold him accountable, not to be destructive, no, but to be constructive.”

Like Sen. Thom Tillis of North Carolina, another retiring Republican, Cassidy is deeply conservative and supports much of the Trump administration’s agenda, including stronger immigration enforcement, deficit reduction and reforms to entitlement programs. Tillis hasn’t shied away from criticizing top Trump administration officials and using his vote to block Trump policies he disagrees with, and Cassidy could follow suit by entering his own YOLO (“you only live once”) era.

“One of the things that makes him such a good doctor is that he’s not emotional in the way that he exercises power,” Sen. John Kennedy, the junior senator from Louisiana, told NOTUS. “He’s very non-emotional in the way he makes his decisions, he’s very analytical, and personally, I think Bill will just continue to do what he’s always done: just call it like he sees it.”

Meanwhile, some Louisiana Republicans said they expect Cassidy to support Trump and his agenda for the remainder of his term. After all, the state’s primary voters sided against Cassidy in large part due to Trump’s endorsement of Louisiana Rep. Julia Letlow in the primary and Cassidy’s vote to impeach Trump. Cassidy also trailed state Treasurer John Fleming, another big MAGA supporter, who will face Letlow in the runoff.

“The way he should navigate his time is do everything he thinks possible to get his state what it’s been asking for and what it needs without any negativity,” Louisiana state Sen. Mike Fesi told NOTUS.

Capitol Hill Republicans are also counting on Cassidy to support Trump’s agenda, including passing billions in additional funding for Immigration and Customs Enforcement this week. Senate Republican leaders can lose no more than three votes on the party-line spending package if all Democrats vote against it, and a handful of Republican senators have already raised questions about a provision in the bill directing money toward the new White House ballroom.

“Cassidy is a team player, and I think he obviously wants to see our team succeed,” Senate Majority Leader John Thune told reporters Monday. “He’s got a lot of things I’m sure that he wants to accomplish in his remaining time here, and I suspect we’ll be working closely with his Republican colleagues to achieve those things and work with us to hopefully help us achieve our broader goals and objectives.”

Cassidy told NOTUS that he wouldn’t join in with knee-jerk opposition to Trump, but that he would continue to stick to his principles.

“If you look at the HELP committee, there’s already been some back and forth regarding nominees,” Cassidy said. “Am I going to deliberately push back on things? No. I’m going to do what’s good for my country and my state.” Reflecting on his time in the Senate and his vote to convict Trump, Cassidy said: “When I die, if that’s put in my obituary — ‘He voted to uphold the Constitution’ — I’ll figure that that’s going to be a better obituary.”