The rookie Republican senator leading the effort to torpedo an agreement with Iran is an Army veteran with a Harvard law degree who has a long record of tough rhetoric against President Barack Obama's foreign policy.

None of Arkansas Sen. Tom Cotton's previous forays into foreign policy raised as many hackles as the letter he authored this week lecturing Iran's leaders on American democracy. This time, 46 fellow Republicans signed onto the document.

Democrats are furious, saying the letter could jeopardize Obama's attempts to get a deal with Iran to limit its nuclear capabilities. Some grouse that Cotton's only been in the fusty Senate for two months. Iowa Republican Sen. Chuck Grassley of Iowa retorted that Cotton is never undecided, and that's a good thing.