The IRS does not care
whose name appears first. However, once you select which name is the
'Taxpayer' and which is the 'Spouse' the IRS wants you to keep the same
sequence year after year.
TTax does not make is easy to simply reverse the order in which your name and your spouse's name appears on the tax return. There are numerous items that are referenced by 'name' spread through out the data file. If you miss changing one of them it will result in an incorrect tax return.
Your only option would be to clear and start over.