Benghazi security: an explosive campaign issue

>>> it's been four weeks since the attack on the u.s. con sue late in libya that killed our ambassador and three other americans. and in this political season, the attack is increasingly becoming a political issue. a congressional committee will hold big hearings tomorrow. a preview tonight from our chief foreign affairs correspondent andrea mitchell .

>> reporter: as house republicans prepare to hold hearings on the benghazi attacks, mitt romney disclosed he met one of the victims, glenn doher doherty.

>> you can imagine how i felt when i found out he was one of the two navy s.e.a.l.s killed.

>> reporter: they met at a christmas party a few years ago. this as the state department rejected request for more security from chris stevens slain in the attacks. washington could say libya was becoming more peaceful. investigators say two months before the attacks, the state department concluded the risk to u.s. personnel was high. republican congressman jason chapis is just bk from tripoli.

>> twice i the simonth leadup, you had bombings in benghazi. and it's 9/11n libya , what other warnings do u need?

>> reporter: there were two assassination attempts against the ambassador in recent months. nbc news lists 230 separate security incidents in libya in 2011 and 2012 . according to eric nordstrom, these incidents paint a clear picture that the environment in libya was fragile at best and could degrade quickly. tonight four republican senators led by john mccain are demanding answers from the cia director and other top intelligence officials in what is becoming an explosive issue. the state department denies it denied the request for more security. tonight four weeks after the attack, the department gave its first blow by blow account of what was clearly a well organized assault, never a spontaneous demonstration as officials first claimed.

>> hearings tomorrow, thanks.