I'm assuming that since 2005 the 2008 Croma still uses the Electro Hydraulic steering.
If you are detecting a long term progressive decline in steering assistance then it is probably not electrical related (bad, lose, corroded power cable connections etc) but probably a decline in the efficiency of the electric hydraulic fluid pump.
You should however get the electrical connections/cable checked as this is a common issue with older/aging Croma's.