Regular readers of this column know we preach that all politics is national, and that Minnesotans' much vaunted independence and willingness to split their tickets are evaporating as national politics has become more polarized.

The 2018 election results supplied plenty of evidence: People in the western suburbs didn't like President Donald Trump, and they often expressed their distaste by voting for DFL candidates across the board, even at the state House level.

This is how the DFL flipped the Minnesota House.

However: This isn't to say candidate quality and campaigns don't matter.

The House DFL flipped 18 seats, but the nine closest races — the ones that really mattered — were decided by an average of 410 votes.

Boots on the ground and a smart strategy to direct them come into play in these close races. With full control of state government at stake in next year's election — with a special eye toward the closely divided state Senate — I'm especially curious to see where some of the most effective outside political groups spend their time and money.

At this point, it's still a bit of a mystery.

The DFL-aligned heavyweight Alliance for a Better Minnesota — backed with the financial muscle of Alida Messinger and a few other big donors — is still sussing out its targets for 2020, spokeswoman Marissa Luna told me.

It smothered former Gov. Tim Pawlenty and then GOP nominee Jeff Johnson with negative ads last year, which smoothed the way for DFL Gov. Tim Walz.

On the Republican side, Gina Countryman, executive director of Minnesota Action Network and who helped the Senate GOP cause in 2016, was coy in an interview last week about the group's plans.

"We're still looking at where we can have the most impact. We don't like to duplicate efforts," she said. Look for a newer group called Advance Minnesota, chaired by former state Sen. Ted Daley and run by GOP operative Emily Nesse, to be a bulwark for Senate Republicans' narrow majority.

John Rouleau of the GOP-aligned Minnesota Jobs Coalition, with a particular focus on data-centric strategies, said his group will play in both state House and Senate races.

Both Countryman and Rouleau said a key phenomenon next year will be massive turnout. They expect turnout on a scale unheard of in recent history, even for Minnesota, which often boasts the highest turnout in the nation. It's difficult to say which side benefits from heavy turnout.

Watch where these outside groups start putting resources, because it will offer an early tell about where the battle will be waged.

• • •

A tweet by University of Minnesota Law School professor/TV talking head Richard Painter must have set off alarm bells in the offices of U.S. Rep. Angie Craig last week: "[Craig] needs to support impeachment or face an independent candidate in MN CD2. Her choice."

Hmm; whatever could he mean?

J. Patrick Coolican 651-925-5042 Twitter: @jpcoolican