Which one ? There’s 3 declared and 1 speculative candidate.
Brian Fitzherbert (R) - Defense Contractor Project Manager, Engineer & ‘18 Candidate
Bob Patterson (R) - Trade Association Executive, Ex-Gubernatorial Aide & ‘16 Nominee in CD-1
David Richter (R) - Venture Capitalist, Ex-Construction Executive & Attorney
(speculative) Seth Grossman (R) - Ex-Atlantic Co Freeholder, Ex-City Councilman, ‘18 Nominee & ‘13 Gov Candidate
But when I went to Bob Patterson, Brian Fitzherbert, and David Richter's websites (not sure which of them is considered the "leading" Republican challenger), they all seem to be significantly to the right of Van Drew and solid conservatives who want to work with the President. Bob Patterson says he was honored to work in the Trump administration, Brian Fitzherbert says President Trump has "done an excellent job of kick-starting our national economy", and David Richter says he's a lifelong Republican who wants to go to Washington to help Trump drain the swamp there.
For comparison:
https://bobpattersonforcongress.com/
https://www.fitzherbertforcongress.com/
https://richter2020.com/
If all three of them stay in the race, its possible they will ironically help Van Drew get the GOP nomination by splitting the anti-incumbent vote.
Van Drew is a traditional reliable RAT vote on a lot of issues (for example, he has always gloated about being strongly pro-abortion). It will be interesting to see if he flip-flops on those issues overnight to market himself in a Republican primary.
Even in a worse case scenario, I agree that Van Drew seems to be an improvement over the RINOish Frank LoBiondo. I always take stuff like that into account, whether the party switcher is an improvement over the previous occupant. LIEberman was awful but the "Republican" he defeated to win his seat was so bad a lot of Republicans cheered on Lieberman. I never warmed to Zig Zag Zell Miller because even on his best day of stabbing "his" party in the back, he was still significantly LESS conservative than the Republican he replaced, Paul Coverdell. It would have been different if Zell Miller had been appointed to replace an odious RAT Senator like Chuck Schumer. If that had been the case, I'd be cheering him on, too.
Oh, and in a final vote, Van Drew switching essentially cancels out that goofball Justin Amash leaving. The difference is that Van Drew is voting the way his constituents want. Amash represents a safe Republican district that voted for Trump and used to be held by Vern Ehlers, so he just voting the way Nancy Pelosi wants in spite of his constituents. I hope that turd gets flushed in the next election cycle.