With the deadline for ratification of the Equal Rights Amendment only nine months away, the National Organization for Women yesterday launched a last-ditch $15 million campaign.

NOW's effort is to be the largest and most concentrated ever undertaken by the 140,000-member feminist group, now celebrating its 15th anniversary. The centerpiece is a national television advertising campaign that could cost as much $8 million.

The bluntly worded ads, which will begin running next week, portray an ERA held hostage by cigar-smoking male politicians.

"A handful of politicians in a handful of states have more votes than millions of Americans," NOW President Eleanor Smeal says in one ad as the camera pans a smoke-filled room. "Nearly two of three Americans want the Equal Rights Amendment. But the politicians control the votes that determine whether ERA becomes part of the Constitution."

She adds, "Should a handful of politicians trade away women's rights?"

After an initial surge in the early 1970s, the ERA drive lost momentum in 1977, and no state has approved it since. To make ERA part of the Constitution, three more states must approve it by next June 30.

NOW's latest "countdown to equality" campaign began here yesterday at the start of the organization's annual convention at the Shoreham Hotel. About 4,000 women are expected at the convention, which is to end Monday in a rally at the Lincoln Memorial with former first lady Betty Ford as the featured speaker.

The convention finds NOW larger and wealthier than ever. Since the election of President Reagan, who opposes the ERA, NOW's membership has grown by 35,000. Smeal opened the convention by telling a news conference that Reagan policies have created a backlash among women that may haunt Republicans at the polls in 1982.

"He is sending a message," Smeal said. "He is against women's rights, and he is slowing down and rolling back all the progress we have made the last 15 years."