Hillary Clinton Jan. 11:

Hillary Clinton is unveiling an aggressive $70 billion stimulus package today that would boost the U.S. economy and help families who have been hit hardest by the economic downturn across America.

Reuters Jan 13:

Amid growing worries about a worsening of the U.S. economy, Democratic presidential candidate Barack Obama proposed a $75 billion economic stimulus plan on Sunday that includes worker tax credits, a one-time pension supplement and help to homeowners facing foreclosure.

The plan would include an immediate $250 tax credit for workers, which could double if the economy worsens, a one-time $250 supplement to Social Security payments ....

The bit about giving Social Security folks--remember seniors have higher voter turnout--is yet another sign that Obama is above average for the politician species.

Hillary Clinton Jan. 17:

Last week, I laid out my blueprint for stimulus of up to $110 billion, including $70 billion in immediate measures and $40 billion in contingent tax rebates.

After seeing additional signs of economic weakness and hearing the stories of countless voters in Nevada, California and across the country, I am convinced that we need my full $110 billion package immediately to effectively stimulate the economy.

Friday, Jan. 18:

As President Bush laid out his vision for an economic stimulus that could reach $150 billion, ...

UPDATE (1/19 9PM): Well that didn't take long--Romney has now upped the ante:

Coupled with a $32 billion program Romney has already proposed to eliminate taxes on all savings for those making under $200,000 annually, the package costs $233 billion — or about 1.7 percent of the gross domestic product.

Romney's proposal is significantly different from the previous plans--it has little in the way of rebates and focuses more on improving incentives. His proposal to reduce the corporate income tax rate is especially noteworthy, albeit not so much for any short run stimulus it would provide.

Romney's plan is more economically literate than the AP reporter who wrote the article on Romney's proposal. The reporter, Glen Johnson, needs to brush up on tax incidence:

[Romney's plan also calls for] an elimination of Social Security payroll taxes for workers over 65 that would cost $20 billion and equally benefit businesses and individuals.