Bill Cotterell

Democrat correspondent

Everybody expects 2018 to bring a “wave election” to Washington, and Florida will be riding the crest of that national trend with probably the most expensive and important U.S. Senate campaign in our history.

Whether that wave is a ripple or a tsunami will depend on one part-time Florida resident, Donald J. Trump. The president has already named his choices for the state’s top two elections – Gov. Rick Scott to beat Sen. Bill Nelson, and Rep. Ron DeSantis to succeed Scott – but will that help or hurt them?

More: Rick Scott mum on Senate run while Bill Nelson prepares for a challenge

Historically, a president’s first mid-term election goes badly for his party. The Republicans gained eight seats in the House and two in the Senate in 2002, but that was right after 9/11 and George W. Bush’s popularity was around 67 percent.

Before that, you’d have to go all the way back to the Great Depression – 1934 – to find a president whose party gained seats Congress halfway through his first term. Franklin Roosevelt was riding pretty high at the time.

By contrast, people keep wondering when Trump will bottom out. If his approval percentage next summer is still mired in the 30s, most Republican candidates will avoid him. Converting the House, requiring a shift of 24 seats, would be in reach for the Democrats.

If that happens, Trump might devote more time to golf, and impeachment, in his the second half of his term.

The Democrats now need to flip only two seats to control the Senate, assuming they hold what they’ve got. A year ago, that seemed unlikely, with the Democrats defending 25 Senate seats (including two independents who caucus with them) and the Republicans having only eight incumbents on the ballot. Making it worse for the Democrats, 10 of their 25 seats were in states like Florida, that Trump had carried last year.

What a difference a year can make – and what a year it has been. The Republicans got off to a fast start, keeping some House seats in special elections to replace members Trump appointed to executive posts. But the Democrats recently elected governors in New Jersey and Virginia, made major legislative gains in the Old Dominion, and this month scored a real stunner – Doug Jones’ victory in the Alabama U.S. Senate race.

Even more ominous for the GOP, Trump had staked some personal popularity on GOP nominees in Virginia and Alabama.

The retirements of Republican Sens. Jeff Flake and Bob Corker put the Arizona and Tennessee seats in play. Nevada Republican Dean Heller is the only GOP incumbent up next year in a state Hillary Clinton won, and he is vulnerable to a primary challenge from his right – the circumstance that spelled disaster for Republicans in Alabama.

Nelson has been telling supporters that the key to control of the Senate for the next two years is Florida. The governor, who is capable of self-financing a statewide race but won’t need to, this time, has been acting like a candidate – getting high marks for his very visible leadership after hurricanes and advancing politically popular spending priorities in his state budget proposals for the 2018 legislative session.

Perhaps only in Florida could someone win five statewide elections and still be relatively untested politically, but Nelson has been blessed with weak opponents. Scott, with his eight years as governor and access to limitless campaign cash, will certainly be the senator’s toughest challenger in a unique campaign climate. But the governor is closely associated with the unpopular Trump, who has promised – or threatened – to campaign actively for GOP nominees next summer.

Nelson benefits from being bland. Scott has been controversial, while still managing to win, but Nelson has never been roundly disliked, as a member of the state Cabinet or in Congress.

There are many unknowables at this point, including the Florida Democratic Party’s truly breathtaking knack for blowing elections. Can the Democrats resist identity politics and field serious candidates? Can the Republicans be sufficiently Trump-like to motivate his base, without reminding everybody of what they don’t like about him?

And how many of those 250,000-plus Puerto Rican citizens who’ve moved to Florida recently will register to vote? And how will they vote?

It’s going to be a fun election year, with Florida right in the middle of it.

Bill Cotterell is a retired Tallahassee Democrat reporter who has covered Southern politics since 1967. He can be reached at bcotterell@tallahassee.com.