Trump is not going to be impeached and removed from office. He'll likely be impeached by the house, but the senate is not going to vote to remove him.
In the modern era, it's very unusual that an incumbent goes challenged in their party primary. The last time it happened in a US presidential election was probably 1968 with Lyndon Johnson, who was considering not running for re-election anyway and was deeply unpopular with his own party because he was the primary escelator of the Vietnam war. Johnson decided not to run as he approached the New Hampshire primary and it was looking like he'd considerably lose.
Meanwhile, in 2019, Trump is unlikely to even have primaries in most states, the GOP just won't run them. In New Hampshire he's being challenged by Bill Weld, but Weld is not likely to get more than a few percent, maybe 10%, in a primary and he's banking entirely on New Hampshire just to play spoiler for the Trump campaign. I believe Mark Sanford already bowed out of the race (who had a similar strategy), right? Weld is banking on the tradition of New Hampshire being a spoiler for the incumbent, whenever an incumbent has been challenge in New Hampshire, they've gone onto lose the general election (the latest being 1992, when Pat Buchanon won about ~40% of the NH Primary, Bush rolled to the convention but Buchanon's criticism of Bush prior to New Hampshire played spoiler for him in the general election).
*Edit*
Actually, I forgot, Ronald Reagan challenged Gerry Ford in the '76 GOP Primary and took it to the convention.
John Dickerson from the Whistlestop Podcast has a great series of episodes on Reagan, Ford, the '76 primary, '76 general, and Ford's VP choice (ultimately ended up being Bob Dole, but it was a shit show and Reagan arguably lost the nomination because he announced his running mate at the primary, a Liberal Republican from Pennsylvania, which shifted Southern conservative Republicans over to the less popular Gerald Ford):
After Ford beat Reagan at the convention, he invited Reagan to speak *after* his acceptance speech, and
Reagan delivered arguably his most memorable speech, which was short, concise, and left delegates feeling like they nominated the wrong candidate.
But Trump isn't being removed from office unless something truly devastating happens in some clear way that signals to Senate Republicans that they have to abandon him. RIght now, there's maybe one or two Senate Republicans that would vote to remove him, maybe Mitt Romney in Utah, but probably not even Romney who will likely say a lot of words and brow beat about how discomforted he is about Trump, but then rally back and say that it's not enough to remove a president, that it's too serious an action for something so inconsequential "As a phone call," which will merely "trouble him." You need at least 20 Republicans, and every Democrat. That's not happening.