Scott Brown rejects Kennedy Institute debate

Scott Brown won’t debate at Kennedy Institute, Marco Rubio won’t be Mitt Romney’s VP, a Republican campaign staffer resigns in Arizona and House members don’t practice what they preached.

Make sure to sign up to get “Afternoon Fix ” in your e-mail inbox every day by 5 (ish) p.m!

EARLIER ON THE FIX:

Marco Rubio isn’t being vetted as VP: What does it tell us?

Reports: Daniels to take top job at Purdue

Romney super PAC airs ‘doing fine’ ad

Mitt Romney’s bus tour — and how he gets to 270 electoral votes

House Republicans add 2012 election ad time in eight media markets

Haley Barbour, radical pragmatist?

Why Republicans can’t write off Hispanics

WHAT YOU MIGHT HAVE MISSED:

* Sen. Scott Brown (R-Mass.) has turned down a debate with Elizabeth Warren (D) at the Kennedy Institute, after Vicki Kennedy refused to stay neutral in the race. Kennedy, the widow of late Sen. Edward M. Kennedy, endorsed Martha Coakley (D) in 2010 days before a debate at the non-profit institute.

* Florida Sen. Marco Rubio (R) isn’t being seriously vetted by former Massachusetts governor Mitt Romney for the VP slot, an outside campaign adviser says. “Only Beth Myers and I know who is being vetted,” Romney told Fox News in an interview airing this afternoon. (Myers, a longtime aide, is leading his VP search.)* The Huffington Post has a long, in-depth analysis of why Gallup polling consistently shows slightly worse numbers for President Obama than other national surveys. The likely explanation: Gallup’s poll weighting underrepresents black and Hispanic Americans.

* An aide to Arizona Republican House candidate Martha McSally has resigned over a report that he helped a Democratic campaign. Staffers for Democratic Rep. Ron Barber told Politico that Sam Stone, McSally’s spokesman, approached a Barber aide with advice on how to beat Republican Jesse Kelly in last week’s special election. McSally is competing for the seat in the fall. If Kelly had won the special election she would have had a tough time getting past the primary; after losing to Barber, he isn’t running again.

* Roll Call notes that some tea party-backed House members who railed against incumbents’ use of congressional mail privileges are now using the system more than most. Reps. Joe Heck (R-Nev.), Frank Guinta (R-N.H.), David McKinley (R-W.Va.) and Bobby Schilling (R-Ill.) all criticized their rivals in 2010 for sending out free mailings to constituents and are among the top 10 users of the service.

WHAT YOU SHOULDN’T MISS:

* The Democratic Senatorial Campaign Committee is making its second independent expenditure of the campaign cycle, and its second in North Dakota. The $85,000 buy is on broadcast and cable, for this ad, which attacks Rep. Rick Berg (R) for voting “to give billions in tax breaks to millionaires while essentially ending Medicare.” Polls suggest Heidi Heitkamp (D) has a chance in this red-leaning state.

* A poll done by Public Opinion Strategies for Deb Fischer’s campaign finds she is well-positioned to win Nebraska’s open Senate seat. State Sen. Fischer, the surprise winner of the GOP primary, leads former senator Bob Kerrey (D) 58 to 33 percent.

* No surprise here: A new WBUR poll finds former Maine governor Angus King, an independent, is the heavy favorite to replace retiring Sen. Olympia Snowe (R). Among likely voters, King takes 50 percent, Secretary of State Charlie Summers (R) takes 23 percent, and state Sen. Cynthia Dill (D) takes 9 percent.

* A Public Policy Polling survey in Arizona shows a dead heat between Rep. Jeff Flake (R) and former surgeon general Richard Carmona (R) for the Senate seat being vacated by Jon Kyl (R), 43 to 41 percent. The same poll has Romney only three points ahead of Obama, 49 percent to 46 percent. Republicans are skeptical, pointing out that PPP is a Democratic pollster.

THE FIX MIX:

Why don’t we have this service anymore?

With Aaron Blake