Today's installment of campaign-related news items from across the country.
* More than five weeks after his guilty plea, Rep. Duncan Hunter (R-Calif.) submitted his resignation letter yesterday. As the Associated Press noted, California Gov. Gavin Newsom (D) "has not said whether he will order a special election or leave the seat open until a successor emerges from the November general election."
* Republican officials in Wisconsin yesterday agreed to exclude Donald Trump's primary rivals from the state's GOP primary ballot. State Republican Parties in Alaska, Arizona, Hawaii, Kansas, Nevada, and South Carolina have done the same thing.
* Trump's re-election campaign is reportedly poised to spend $10 million to advertise during the Super Bowl, and according to Politico's report, the message is "expected to run early in the game, when viewership is likely to be at its highest." (It's unclear whether Team Trump will air one 60-second commercial or two 30-second commercials.)
* Michael Bloomberg's Democratic presidential campaign also announced yesterday that it, too, has bought Super Bowl ad time, investing $10 million in a 60-second spot.
* The next debate for Democratic presidential candidates is six days away, but DNC Chair Tom Perez said yesterday that if the presidential impeachment trial is underway, the party is prepared to postpone the event. Of the five candidates who've qualified to participate, three are sitting U.S. senators.
* An amazing campaign-finance statistic: Tom Steyer's Democratic presidential campaign has spent more on advertising than 12 of the other Democratic candidates combined. Michael Bloomberg's campaign, meanwhile, has more than doubled Steyer's ad spending.
* And while Joe Biden leads the Democratic field with 31 congressional endorsements, McClatchy News made a notable observation yesterday: at this point four years ago, Hillary Clinton had 181 congressional endorsements.
MORE: Today's Maddowblog