Sunday's election, which witnessed a very low turnout of about 35 per cent, had been dominated by anxiety over the global financial crisis.
Two polls late on Sunday, which had been highly reliable in past elections, said that the Social Democrats had come first, but by early morning the outcome was less clear.
Under Romania's constitution, it will be Basescu's job to name a prime minister, with parliament voting whether to validate his choice.
The two opposition parties are now set to spar over who heads the next cabinet.
The Democratic Liberal party are likely to have an upper hand because of their links with Basescu.
However, coalition talks may now depend on the PNL, which is likely to play the role of kingmaker if it forges an alliance with one of the bigger parties.
Mircea Marian, a commentator for the Evenimentul Zilei newspaper, said: "The PNL is in an excellent position now. It can negotiate with anybody. It can even get the prime minister post."
The results showed the ethnic Hungarian Party with more than 6 per cent of votes.
The election also cemented the demise of Romania's ultra-nationalist politician Corneliu Vadim Tudor, who failed to make it into parliament for the first time since the fall of communism.
He was Nicolae Ceausescu's, the former president, court poet.