In a sign that former Massachusetts Governor Mitt Romney is taking serious the campaign of rival Republican presidential candidate Mike Huckabee, Romney has unleashed a volley of criticism of the candidate who is emerging as Romney's chief opponent for the GOP presidential nomination.

Romney, who refrained from attacking Mike Huckabee until public polling showed the ex-Arkansas guv with a growing lead in the presidential campaign, is hitting Huckabee on the issue of taxing and spending. On a press release posted on Mitt Romney's official campaign website, Romney details media criticism of Huckabee's ten-year record as chief executive of Arkansas.

See Romney's pointed critique here.

On Saturday, the Romney campaign reprinted and distributed a column penned by Ernie Dumas, editorial writer for the Arkansas Leader newspaper. Dumas' op-ed stated "Mike Huckabee raised more taxes in 10 years than Bill Clinton did in his 12 years."

See the Dumas editorial here.

This is Mike Huckabee's response to Dumas and Mitt Romney's promotion of the Dumas piece on the Romney Campaign website.

In summary, the once-sleepy and congenial race for the Republican Party presidential nomination is heating up significantly. Watch for continued attacks and responses from the FIVE leading candidates against each other, as polling suggests that the race for the GOP nod is wide open.