Prior to the 2016 presidential election, Jeb Bush, son and brother to two former U.S. presidents, was among the Republican Party (GOP) lawmakers pursuing the GOP’s presidential nomination. Name recognition may have been on his side had another man with TV notoriety not entered into the race.

Donald Trump would go on to secure the primary and ultimately the election, leading to a controversial administration with fervent support from some people and equally intense opposition from others. Even within the GOP, some supporters struggled to cope with Trump’s approach to national politics which can, at times, seem to lack overarching strategy or the usual fit and finish Americans have come to expect from their executive branch.

Trump’s policy decisions and public statements are often the subject of debate, even within his own party. For instance, a dozen Republican senators sided with Democrats last week to overturn the president’s declaration of a national security emergency along the U.S. southern border in order to secure funding for a wall.

The president’s remarks about the late senator and former prisoner of war John McCain also led to some conservatives breaking rank with their party. McCain and Trump publicly didn’t see eye-to-eye on a number of initiatives, prompting the president to attack the senator over his standing as a “war hero.”

“He’s not a war hero,” Trump said during his presidential run. “He was a war hero because he was captured. I like people who weren’t captured.”

The president’s distaste for McCain didn’t simmer after the senator’s death, with another recent tweet targeting the late Arizona Republican from earlier this week once again stirred unrest among Republicans that either favored McCain or that see public attacks on his character after his death as inappropriate.

Traditionally, a sitting president is seen as the defacto head of the political party that saw him elected in the first place. Sitting presidents are expected to run for re-election and, for the most part, don’t even need to worry about the primaries. This may not be the case for Donald Trump. Bush, a former two-time Republican governor for the state of Florida, publicly called for someone within the GOP to challenge Donald Trump for the party’s nomination in the 2020 election.

“I think someone should run just because Republicans ought to be given a choice,” Bush said of his former GOP opponent in a recent interview with CNN. “It’s hard to beat a sitting president, but to have a conversation about what it is to be a conservative, I think it’s important.”

Bush seemed to take swipes at Trump’s “Make America Great Again” campaign slogan in his remarks, saying Republicans need a candidate that’s looking forward, rather than back.

“And our country needs to have competing ideologies that people…that are dynamic, that focus on the world we’re in and the world we’re moving toward rather than revert back to a nostalgic time,” he continued.

Bush was also critical of Trump’s approach to foreign policy, seemingly echoing some of the concerns laid out by James Mattis when he resigned his position as the Trump’s Defense Secretary, citing concerns about Trump’s aggressive approach to allies and friendly approach to diplomatic opponents.

“We haven’t had a major crisis to deal with, but this unilateralism or going-alone-ism I think is really dangerous,” Bush said. “Our friends no longer believe they can trust the United States and our enemies, in many cases, feel emboldened by this approach. I think it defies the…bipartisan kind of consensus on foreign policy that has, by and large, kept America safe.”

Whether or not Bush will find support within his party for a Republican challenger to Trump’s re-election is unknown.