The likelihood of Mrs Elizabeth Dole entering the 2000 presidential race has put pressure on other Republican hopefuls to declare their intentions.
Opinion polls have shown that Mrs Dole, who campaigned actively for her husband, Mr Bob Dole, in the 1996 presidential election, would be strongly supported by Republican voters if she ran for the presidency.
Mrs Dole, who is a youthful-looking 62, announced this week that she is resigning from her post as president of the American Red Cross, saying: "I believe there may be another way for me to serve our country."
In a farewell address to Red Cross staff, Mrs Dole said: "Soon I will be considering new paths and there are exciting possibilities. I will choose one and pursue it with all my might."
She later told reporters she had not yet decided to run for president but she was "going to give it serious consideration".
Up to now, Mrs Dole has insisted that she was not interested in the Republican nomination for the presidency, but observers now believe she has changed her mind.
Her advisers are said to have planned how she can raise $22 million this year for her campaign. An exploratory committee for fund-raising may be announced in two weeks' time when she formally stands down from her Red Cross post.
As Mrs Dole made her resignation announcement, another Republican contender, Senator John Ashcroft of Missouri, indicated that he would not seek the nomination for which he has been working for much of last year. Instead he will concentrate on holding off a strong Democratic challenge for his Senate seat.
But a new Republican contender, Senator Bob Smith of New Hampshire, has announced that he is seeking the nomination. His main appeal will be to the conservative and religious wing of the Republican party which was disappointed with Mr Bob Dole's moderate anti-abortion stance in the 1996 election.
The leading Republican contender for the nomination is still Governor George W. Bush of Texas, son of former president George Bush, although he has not yet formally declared. Others interested in running are former Vice-President Dan Quayle of Indiana; Senator John McCain of Arizona; wealthy publisher Mr Malcolm Forbes; former Governor of Tennessee Mr Lamar Alexander; and Mr Gary Bauer, a conservative who heads a family rights organisation.
If Mrs Dole enters the race, she will obviously appeal to many women voters who may feel it is time there was a woman president in the White House. During the 1996 campaign, Mrs Dole said in an interview: "I really believe this country's ready for a woman president."
But, she continued, "it will probably happen through a woman running for vice-president rather than someone just jumping in and running for president. Although that could happen too. I think we'll see it fairly soon."
Mrs Dole actually had higher popularity ratings than her husband and his running mate, Mr Jack Kemp, during the 1996 campaign. She was the star turn at the Republican convention that year when she stepped down from the platform and walked among the delegates with a clip-on microphone praising her husband's qualities.
Mrs Dole has impressive qualifications in her own right. She is a graduate of Harvard Law School and went to Washington where she worked for the White House Office of Consumer Affairs and the Federal Trade Commission before being appointed to President Reagan's cabinet as Secretary for Transportation.
She then served in President Bush's cabinet as Secretary for Labour but resigned in 1981 to head the Red Cross, for which she raised $3.5 billion.
Reuters Add: Among Democrats, the situation seems less complicated. Vice-President Al Gore is the overwhelming favourite. His only challengers at this point are former New Jersey Senator Bill Bradley and Minnesota Senator Paul Wellstone, but most Democrats and independent analysts believe it would take a political earthquake to deprive Mr Gore of the nomination.
Republican sources said Mrs Dole's move puts pressure on Mr Bush to speed up his own presidential timetable. He had earlier indicated that he would not begin a campaign until after the upcoming session of the Texas legislature, which ends in May.
A Dole candidacy would inject a new element into US politics, where women have increasingly been supporting Democrats in recent presidential polls.