 -- Republican Sen. Ben Sasse, a longtime vocal critic of GOP presidential candidate Donald Trump, is calling for voters to rally around a third-party candidate capable of winning the White House.

In an open letter on Facebook, Sasse said that conversations with residents in his home state of Nebraska have convinced him that many voters would be open to an additional option besides Trump and likely Democratic nominee Hillary Clinton.

“Why shouldn’t America draft an honest leader who will focus on 70% solutions for the next four years? You know ... an adult?” he asked.

“I believe that most Americans can still be for limited government again -- if they were given a winsome candidate who wanted Washington to focus on a small number of really important, urgent things -- in a way that tried to bring people together instead of driving us apart,” he continued.

In order to catch the two front-runners quickly, Sasse, 44, recommended this new candidate be someone who can “campaign 24/7 for the next six months. Therefore he/she likely can’t be an engaged parent with little kids,” describing himself and several other people who've been mentioned, including House Speaker Paul Ryan.

Nor, he said, should lawmakers apply “an ideological purity test” to the candidate because he or she would “almost certainly be more conservative than either of the two dishonest liberals now leading the two national parties.”

While many of Sasse’s fellow lawmakers have expressed skepticism of Trump, the Republican senator mostly stands alone in his public desire for a third-party candidate to compete alongside the likely Republican nominee.

This isn’t a new position for Sasse, although he appeared compelled to reiterate it after Trump won the Indiana primary earlier this week and moved that much closer to clinching the party’s nomination.

Sasse wrote a Facebook post in February, saying, “If Donald Trump ends up as the GOP nominee, conservatives will need to find a third option.”