FRIDAY’S CAMPAIGN ROUND-UP…. Today’s installment of campaign-related news items that wouldn’t necessarily generate a post of their own, but may be of interest to political observers:

* In Wisconsin, Republican-aligned groups have filed recall petitions against three Democratic state senators, but the state Democratic Party intends to challenge the legitimacy of those petitions, on the grounds that many were collected improperly. (There are reports, for example, of conservatives trading alcohol for signatures in at least one location.)

* Nate Silver has a fascinating chart, measuring media coverage by month for each of the potential presidential candidates in the Republican field. In November and December, Sarah Palin dominated; in March, Newt Gingrich received a narrow plurality; and so far in April, Donald Trump has generated more coverage than most of the other candidates combined.

* Speaking of Nate, it’s widely assumed that in Nevada, Rep. Dean Heller (R) will be tapped to replace Sen. John Ensign (R). But will that automatically give Heller an edge when seeking a term of his own next year? Not necessarily.

* In Florida, the Republican field of candidates hoping to take on Sen. Bill Nelson (D) next year keeps growing, with state Rep. Adam Hasner (R) officially filing his paperwork yesterday. State Senate president Mike Haridopolos is generally considered the Republican frontrunner, but he’s plagued by ethics scandals, among other problems.

* Former New Mexico Gov. Gary Johnson (R), during his first week as a presidential candidate, argued that because Americans “elected a black president,” it proved “we are colorblind.” He added, “Colorblind and we’re not a discriminate [sic] nation.”

* Former Minnesota Gov. Tim Pawlenty (R) used to support storage of nuclear materials in Yucca Mountain in Nevada. Now that he’s a presidential candidate hoping to compete in Nevada, Pawlenty’s views on the policy are evolving.

* In Arizona, Rep. Jeff Flake (R) is running for the Senate, so his House predecessor, former Rep. Matt Salmon (R) hopes to take back his old seat. Salmon left Congress in 2000 due to self-imposed term limits.

* And in Virginia, the Republican field of U.S. Senate candidates keeps growing, with Timothy E. Donner, a Northern Virginia television production company owner, launching a campaign this week. The GOP frontrunner, former Sen. George Allen, is delighted to have so many Republican opponents, because it dilutes the field and makes it easier for him to get the nomination.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.