Jonathan Gruber on the hot seat heading into hearing

Republicans in Congress plan to launch its final assault on Obamacare as consultant Jonathan Gruber will face questions about possible deceptions and a lack of transparency in the 2010 Affordable Care Act Monday.

Lawmakers have obtained videos that show Gruber saying the law was written in a 'very tortured way' to hide taxes and passed because of the 'stupidity of the American voter.'

Rep. Darrell Issa, chairman of the House Oversight Committee told Reuters the public deserves an explanation from Gruber. Issa has used his position to attack the administration on issues such as the IRS scandal, misplaced guns and U.S. deaths in Benghazi.

If you can't trust what he says, and what he says he'll do, to get votes and trick the American people into voting for something, then can you trust his analytics?' Issa said of Gruber.

'It is our job to see that the administration is working to run the country and that they are reporting honestly their successes and their failures,' he told Reuters.

Like many congressional hearings, Tuesday's session may provide partisan fireworks while doing little or nothing to change government policy. The president says he will veto any effort to overturn what Republicans call 'Obamacare,' should such a bill reach his desk after Republicans add Senate control to their House majority next year.

Gruber has served as health care adviser to former Massachusetts Gov. Mitt Romney and has been dubbed 'architect' of Obamacare by some Republicans. The government paid Gruber nearly $400,000 for his work.

Also testifying Tuesday will be Marilyn Tavenner, administrator of the Centers for Medicare and Medicaid Services. In an effort to distance Tavenner from Gruber's remarks, the administration asked Issa to put her on a different witness panel. Issa's staff said it was weighing the request.

Issa calls the health care law 'the poster child for this administration's broken transparency promises.'

Issa's bare-knuckled inquiries into administration policies and missteps have often infuriated Democrats while providing welcome fodder for conservative talk shows, speeches and campaigns.

Issa has clashed with the administration on numerous topics. When he accused it of improper campaigning, he tried to bring two former Cabinet members - former Health Secretary Kathleen Sebelius and former Labor Secretary Hilda Solis - before his committee. They declined.

Reuters and news3blog.blogspot.com contributed to this report