Senator Elizabeth Warren and Representative Geoff Diehl met Sunday night for the second time to debate who should represent Massachusetts for the next six years.

Senator Warren must be wondering why she ever listened to the people who advised her to debate her Republican opponent. She has a tremendous lead in the polls. She has virtually unlimited campaign cash on hand. The political issues that are motivating base voters in both political parties are in her favor this year in Massachusetts. She is an incumbent Democrat in Massachusetts. Incumbent Democrats in Massachusetts lose elections due to grand juries, not due to Republican challengers.

I give Sen. Warren a tremendous amount of credit for agreeing to debate Rep. Diehl multiple times. She could have refused to debate him, and she would have caught some flack for it from the media, but it wouldn't have had any impact on her election or her future plans.

President Lyndon Johnson refused to debate Sen. Barry Goldwater, and President Richard Nixon denied Sen. George McGovern the opportunity to share the stage with him. Both McGovern and Goldwater were respected members of the U.S. Senate and the official candidates of their political parties for the presidency. However, Nixon and Johnson understood they were the required ingredient for a debate to happen, and they knew they would only be sharing their spotlight with their political enemy if they agreed to debate.

Johnson and Nixon went on to defeat Goldwater and McGovern. Things didn't go so well after their victories, but that had nothing to do with shunning their opponents.

Diehl has run a great campaign against incredible odds. He beat two other strong candidates to become the GOP nominee against Warren. He has sacrificed a safe seat (and the salary and benefits of that job) in the Massachusetts House of Representatives to bring his message of tax cuts, economic growth, and law and order to this election. He has been traveling the Commonwealth in his RV with a small group of dedicated supporters for more than a year.

As hard as Diehl and his team worked, they still needed one more thing to happen for his campaign to have any chance at success. Despite his successful campaign to roll back the gasoline tax, despite the endorsements of powerhouses like Bristol County Sheriff Thomas Hodgson and Governor Charlie Baker, and despite winning the Republican primary, he still needed one more thing to be considered a credible candidate against Sen. Elizabeth Warren.

He needed Warren to acknowledge him as a legitimate and credible opponent by agreeing to debate him, and by attacking him in those debates. Diehl looks and sounds like a U.S. Senator on the stage with the actual U.S. Senator he is looking to replace.

The biggest donor to Diehl's campaign turns out to be Elizabeth Warren, because she donated to him her spotlight.

Chris McCarthy is the host of The Chris McCarthy Show on 1420 WBSM New Bedford. He can be heard weekdays from 10 a.m. to noon. Contact him at chris.mccarthy@townsquaremedia.com and follow him on Twitter @Chris_topher_Mc. The opinions expressed in this commentary are solely those of the author.