After more than a year of frenetic efforts, the Iowa caucuses campaign has hit the home stretch. With just one month until the Democratic nominating process formally begins on Feb. 3, here are some things to watch:

Changes in the polls. As 2020 starts, polling averages show a tight four-way Iowa race among former Mayor Pete Buttigieg, Vermont Sen. Bernie Sanders, former Vice President Joe Biden and Massachusetts Sen. Elizabeth Warren with Minnesota Sen. Amy Klobuchar registering some recent gains. But history shows the last month often produces dramatic shifts.

Polls to ignore for the next month: national surveys. They’ll change, perhaps dramatically, after the Iowa results are in.

The Jan. 14 Des Moines Register debate. The last major televised confrontation before the caucuses will provide an indication of how the contenders view their standing — and could give one or another some well-timed momentum.

Last month’s debate indicated some rivals believe the top target is Buttigieg, the unexpected contender whose term as South Bend, Ind., mayor ended Wednesday. But they need to be careful; Democrats often react badly to negative campaigning.

The Des Moines Register endorsement. A definite boost for the recipient, though no guarantee of victory.

Senate’s impeachment trial. Even harder to figure. A lengthy trial could keep Sens. Sanders, Warren, Klobuchar and Cory Booker from campaigning in the state, leaving the field to Biden and Buttigieg.

But a highlight moment during Trump’s trial could boost one of the senators tied down in Washington.

Who is going negative and what does it mean? A tricky consideration.

Trumpian interference. A potential for mischief. The president is essentially unopposed for re-nomination in the GOP caucuses, since his two rivals, Joe Walsh and Bill Weld, are concentrating on the Feb. 11 New Hampshire primary.

But that won’t keep Trump, possibly with an eye on November, from appearing in the state or training his own unique political criticism on Biden or another of his potential Democratic rivals. He’s scheduled a Milwaukee rally the night of the Des Moines Register debate.

Unpredictable turnout. The intensity of the Democratic campaign and strong anti-Trump feelings mean a record is likely, surpassing the estimated 238,000 Democrats who caucused in 2008, when Obama defeated Edwards and Clinton.

One uncertainty is how a big turnout will influence campaigns like Warren and Buttigieg that have invested most heavily in the organizations that have proved crucial in the past.

But a related factor is how a big turnout affects the ideological makeup of the caucus electorate. Traditionally, low turnouts have been thought to favor each party’s activists, Democratic liberals and Republican conservatives. But recent polling shows Iowa Democrats as a whole are more moderate than perceived, meaning a large turnout could favor the more moderate hopefuls — Buttigieg, Biden and Klobuchar — over the more liberal ones — Sanders and Warren.

How many winners? The traditional analysis is there are three tickets out of Iowa; while the winner gets a boost, so might an unexpected runner-up or a surprise third-place finisher.